There are a number of booklet binding systems presently being manufactured and sold on the market today. These include continuous spiral binders, wire loop binders, and resilient plastic binders.
The resilient plastic binders include a specific construction which is identified by the term "plastic comb" which employs a mechanical spreading device for retracting the curved fingers away from a back connecting bar to permit insertion of the fingers through the pre-punched sheets and then releasing the spreading device to close the back connecting bar around the fingers and capture the sheets on the fingers. Except for conventional split ring loose leaf binders, all of the present systems are constructed to permit only assembly of the paper sheets on the binding apparatus with the aid of a holding and/or spreading device and do not permit the sheets to be readily removed or additional sheets to be added to the bound booklet, without such a device.
Presently, wire loop binders require the opposed loop segments to be forcibly bent together with the aid of a special holding and bending device after the paper has been assembled thereon so that it is impossible to add sheets after the original assembly process.